index.js

const electron = require('electron');

const app = electron.app;
const BrowserWindow = electron.BrowserWindow;

let mainWindow;

function createWindow() {
  mainWindow = new BrowserWindow({
    width: 900,
    height: 600,
  });
  mainWindow.loadURL(`file://${__dirname}/index.html`);
  mainWindow.on('closed', () => {
    mainWindow = null;
  });
}

app.on('ready', createWindow);

// Quit when all windows are closed.
app.on('window-all-closed', () => {
  // On OS X it is common for applications and their menu bar
  // to stay active until the user quits explicitly with Cmd + Q
  if (process.platform !== 'darwin') {
    app.quit();
  }
});

app.on('activate', () => {
  // On OS X it's common to re-create a window in the app when the
  // dock icon is clicked and there are no other windows open.
  if (mainWindow === null) {
    createWindow();
  }
});